C++-字符与字符数组-接收一个英文字符，判断该字符是大写或小写，若是大写输出该字符的小写形式，反之亦然
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Background
Description
接收一个英文字符，判断该字符是大写或小写，若是大写输出该字符的小写形式，反之亦然。
Format
Input
Output
Samples
A
a
t
T
